Wind turbine rotor blades may be manufactured using a technique such as the closed-mould casting technique in which the entire blade can be moulded. Glass fibre matting can be used to build up component layers in a suitably shaped mould, and the layers of matting are bonded with a resin and cured in the mould to give a fibre-reinforced polymer or glass-reinforced plastic, generally referred to simply as ‘fibreglass’. Such a method is described in EP 1 310 351 A1.
To facilitate releasing the finished fibreglass component after curing, the mould is usually coated with a release agent such as a suitable wax so that the resin does not bond with the mould. The release agent is applied to the mould before building up the fibreglass layers. Known release agents are polyvinyl alcohol, silicone wax, slip wax, etc. The release agent must be applied in a uniform layer, and this layer must be absolutely smooth if the outer surface of the cured blade is also to be smooth. However, it is not easy to apply the release agent so that these requirements are met, and the result can be an uneven or dimpled component surface. Furthermore, the types of release agent generally used contain volatile solvents, which pose a health risk to anyone exposed to them. However, the main disadvantage of having to use such a release agent is that, after curing, remnants of the release agent can adhere to the blade in places. These remnants of release agent must be removed in a time-intensive procedure such as scrubbing or sandblasting, adding to the overall cost of manufacture.